It has become perhaps the most famous question ever asked in American public life: "What did the president know ... and when did he know it?" Tennessee's Senator Howard Baker, the ranking Republican member of the Senate Select Committee on Presidential Campaign Activities, echoed the frustration of the nation in 1973 as a parade of witnesses before TV cameras told a complex, shadowy tale of intrigue, intimidation, electronic surveillance, and payoffs at the highest levels of government. The flood of sordid revelations became popularly known as the Watergate scandal, and the resulting congressional investigations, court actions, newspaper accounts, and books would fill a small research library. But has the senator's question ever been satisfactorily answered?

The wrenching experience that President Gerald Ford would call "our long national nightmare" began as low farce. At 2 A.M. on June 17, 1972, five men were caught rummaging through the Democratic National Committee's headquarters in the Watergate complex in Washington. Carrying cameras and electronic surveillance equipment, they had already removed ceiling panels and riffled through party files. All the men turned out to have connections with the Central Intelligence Agency. They had been caught only because an alert security guard noted that they had taped over a door lock. When he removed the tape, one of the burglars retaped it, apparently suspecting nothing.

At the time President Richard Nixon, the Republican standard-bearer, seemed headed toward an easy reelection victory over the Democratic nominee, Senator George McGovern. Even when one of the burglars turned out to be James McCord, a security agent for the Committee for the Reelection of the President (CRP), Nixon asserted that "the White House has had no involvement whatever." But Lawrence F. O'Brien, the Democratic national chairman, denounced the raid as "a blatant act of political espionage" and filed a $1 million lawsuit against CRP. Meanwhile, more and more lines of investigation led toward the White House. Two of the burglars were linked to E. Howard Hunt, the CIA operative in charge of the embarrassing attempt to invade Cuba in 196 1. Hunt had recently been advising Nixon's special counsel and longtime political strategist, Charles W. Colson. Even as the FBI, Department of Justice, Congress, and reporters began to focus on this inexplicable story, the president succeeded in attaining a stunning reelection victory in November.

Yet, as Nixon and his staff celebrated, the growing Watergate puzzle was becoming a national obsession. The president was soon preoccupied with explaining each bizarre new twist of the plot. Had he and his people somehow sown the seeds of their own political destruction?

"Plumbers" for National Security

On May 9, 1969, only a few months after Richard Nixon had taken the oath of office for his first term, he became infuriated when The New York Times reported that the United States was secretly bombing North Vietnamese bases in Laos and Cambodia. Wiretaps were ordered for the telephones of suspected informants.

Two years later, on June 13, 1971, the same newspaper began publishing excerpts from a confidential Pentagon report about the country's involvement in Vietnam. Clearly, a government insider had passed along the 7,000-page study, for only 15 copies existed. Eventually, it was learned that the report had been leaked by Daniel Ellsberg, formerly an analyst for the Department of Defense.

Determined not to have the private deliberations of his own administration noised abroad in this way, Nixon conferred with his two closest and most trusted advisers, White House Chief of Staff H. R. Haldeman and Domestic Affairs Adviser John D. Ehrlichman. Their solution was to order Egil Krogh, Ehrlichman's chief assistant, to establish a secret group charged with "plugging leaks." Inevitably, they called themselves "the plumbers. " Hunt and a former small-town prosecutor and gun fancier named G. Gordon Liddy joined this enterprise but bungled their first assignment. Hoping somehow to discredit Ellsberg, they hired anti-Castro Cubans to break into the office of his psychotherapist, but the misguided burglars failed to find his treatment files.

Preparing for the Worst

In 1960 Nixon had narrowly lost the presidential election to John F. Kennedy. In his 1968 comeback he had narrowly beaten Hubert Humphrey. Pollsters said at the time that the trend of voter opinion was moving against him so swiftly to ward the end of the campaign that he could have lost if the election had been held only a few days later. To consolidate what he feared to be a tenuous political position, Nixon established CRP, an organization dedicated to raising the millions of dollars that would fund an impressive reelection campaign in 1972. John Mitchell resigned as attorney general to become director; Liddy was hired as financial adviser; McCord was named head of security.

CRP was dramatically successful, amassing a huge war chest from corporation executives who undoubtedly wanted to be remembered at the White House after the election. But, even as it became clear that the Democrats would nominate a candidate who had almost no chance of defeating the incumbent, some operatives apparently felt that unusual measures were necessary.

To this day, it is not known exactly what the burglars hoped to find at the Democratic headquarters on June 17, 1972. Did they have reason to suspect that their opponents had information that could scuttle the juggernaut of the Nixon campaign? Did they hope that "bugging" the offices would help them anticipate Democratic strategies? Ironically, the burglary attempt itself would prove to be the most damaging event of the campaign, a time bomb that would not detonate for months to come.

The Net Begins to Close

For a time, the Watergate story moved to the back pages of newspapers, but Ehrlichman, Haldeman, Mitchell, and a young lawyer named John Dean, special counsel to the president, fully recognized its explosive potential. They were working frantically to buy the silence of Hunt, Liddy, and the five original burglars. All had been promised presidential pardons, but McCord pressured by a tough district court judge, John Sirica - confessed in March 1973 that Dean and Jeb Magruder, formerly a deputy director of CRP, had prior knowledge of the break-in.

Only a month earlier, the U.S. Senate had set in motion an investigation that would lead to nationally televised hearings into the affair. There followed a veritable avalanche of charges, countercharges, rumors, and threats. Eventually, Dean cooperated with the Senate panel, portraying a White House that was deeply involved in covering up the Watergate story. He stated that Mitchell had been urged to "take the heat" by confessing responsibility for the burglary; that Nixon knew that Hunt was asking for more than $120,000 to keep quiet about his activities; and that Ehrlichman tried to have evidence destroyed. Dean also revealed that Haldeman had ordered an aide to "remove and destroy damaging materials" from White House files.

At the heart of Dean's testimony, as if aimed in the direction of Senator Baker's fundamental question, was Dean's contention that the president had lied to the American public about his own involvement in the case, Testifying with calm precision, the self-possessed young lawyer charged that Nixon knew about the cover-up at least as early as September 15, 1972. The president had claimed that he learned about it more than six months later, on March 21, 1973, and had immediately ordered a search for the whole truth. Actually, said Dean, his boss already knew the entire story by then and was directing his energies toward saving himself.

Not surprisingly, Nixon fired Dean and regretfully asked for the resignations of his two senior advisers, Haldeman and Ehrlichman.

The Skirmish of the Tapes

Quite by accident, Senate investigators discovered that Nixon had installed a tape recorder in the Oval Office. Stored in basement archives, the tapes covered conversations dating back to the spring of 197 1. Immediately, the special prosecutor appointed by the Justice Department, a Harvard law professor named Archibald Cox, cooperated with Judge Sirica and the Senate committee in efforts to obtain the taped evidence. Again citing executive privilege, Nixon refused to surrender the material and tried to force Cox, whom he called a "partisan viper," to desist. Cox, having been promised independence from the government, refused. Nixon's response was to order his dismissal on October 20, 1973.

Attorney General Eliot Richardson resigned rather than carry out the president's order. Then his deputy resigned as well. Although purposely timed to occur on the weekend, when public reaction might be muted, the action provoked, to use the term of Nixon's new chief of staff, General Alexander Haig, "a firestorm."

The Incriminating Tapes

Stunned, Nixon backed down. Of the nine tapes sought by investigators, however, he produced only seven, one of which fell suddenly silent for a gap of 18 minutes. The president's loval secretary, Rose Mary Woods, claimed that she bad inadvertently erased that section by resting her foot on a control button. When she tried to demonstrate the maneuver to reporters, however, she was unable to do so. Other gaps throughout the tapes were, in many cases, electronically enhanced by technical experts.

Therefore enough incriminating material was clearly audible, causing one of Nixon's own lawyers to whisper, upon hearing the tapes for the first time: "It's all over now." Nixon was taped in a discussion of the cover-up on June 23, 1972, only six days after the burglary and a date much earlier than that reported by John Dean.

In July1974 the U.S. Supreme Court unanimously affirmed the right of courts to hear other tapes. The House Judiciary Committee, which had begun an impeachment inquiry, was given 19 tapes, but it wanted 42 more, covering conversations held between June 1972 and June 1973. The committee issued the first subpoena ever handed a president during impeachment proceedings.

Eventually, the White House released the tapes and approximately 1,200 pages of transcripts from them. Nixon explained that, because of vulgar language and national security matters, the transcripts would be edited versions rather than verbatim accounts. When the extent of the editing became known, and the transcripts were compared with the actual tapes, his credibility was further eroded.

The House committee, after public hearings, voted on July 30, 1974, to report three articles of impeachment to the full House of Representatives: obstruction of justice, abuse of the powers of the presidency, and attempts to impede the impeachment process itself Two other articles were rejected.

In the National Interest

As late as August 5, Nixon was publicly assuring the nation that the record of the Watergate affair and his actions did not justify the extreme step of resignation. Grim reality intervened, however. Some of Nixon's oldest political friends and supporters, including the conservative senator Barry Goldwater, warned him that he was likely to be impeached by the House. Only resignation, they advised, could prevent the shameful spectacle of a subsequent trial before the entire Senate.

Thus, on the night of August 9, Nixon went on national television to announce that he would resign at noon the following day. Far from admitting any guilt or sense of remorse, he explained that his decision had become necessary only because he lacked a political base in Congress.

In an indictment that would lead to the conviction and imprisonment of many of his followers, including Mitchell, Haldeman, and Ehrlichman, the president himself was designated an "unindicted co-conspirator." The threat of prosecution lay over him until his successor, President Ford, proclaimed an amnesty "for all offenses" against the United States that Nixon may have committed during his presidency.

Ford's genial rectitude had brought him immediate popularity in the White House, but this act - which may have been motivated entirely by compassion for a disgraced and depressed human being -was viewed with suspicion by many. Some analysts think that it greatly contributed to Ford's defeat by Jimmy Carter in 1976. Although Ford hoped "to firmly shut and sea] this book" by granting the pardon, in fact he added yet another fillip to the mystery. Did Nixon agree to resign only on the condition that he be promised a pardon? There is no evidence that Ford was party to any such deal, but the legacy of Watergate was a heightened distrust of high public officials. In the absence of proof, some voters seemed willing to believe the worst.